Duke Nukem Forever is probably gaming's biggest example of vaporware (vaporware's a term used to describe games that are in development for so long that people just assume they're never going to be made).
The game was announced back in 1997 for the PC, and has spent 12 years in development, being juggled between different studios, designed, then re-designed, then re-designing the re-design to accommodate the updated computer technology; going from about 3 or 4 different game engines, and all that crap. On May 6 the studio that was in charge of it shut down due to a lack of funding.